Nucleoside uptake by red blood cells from a primitive vertebrate, the pacific hagfish ( Eptatretus stouti), is mediated by a nitrobenzylthioinosine-insensitive transport system

Abstract

Red blood cells from the Pacific hagfish ( Eptatretus stouti) were found to possess a facilitated diffusion nucleoside transport system insensitive to inhibition by the nucleoside transport inhibitor nitrobenzylthioinosine (NBMPR). Uridine uptake by this route was saturable (apparent K m 0.14 mM; V max 2 mmol/l cells per h at 10°C), inhibited by inosine and adenosine, and blocked both by the vasodilator dipyridamole and by the thiol-reactive agent p-chloromercuriphenylsulphonate. The properties of this carrier resemble closely those of NBMPR-insensitive nucleoside transport systems in some mammalian neoplastic cell lines and in rat red cells. The presence of this type of carrier in a primitive vertebrate suggests that such transporters have a broad biological distribution and that they pre-date or arose at an early stage of vertebrate evolution.